When it comes to aviation safety, every event, from taxiing to parking the aircraft, should be treated with an equal amount of respect and attention to detail. While most consider the flight to be over as the plane approaches the apron, mistakes involving the parking brake may result in significant damage and expenses. Although the majority of aircraft use chocks placed by ground crew members to park the vessel in the correct place, there are several circumstances where the tarmac is off-limits for personnel. Additional cases where parking brakes are employed to maintain aircraft position include deicing, ramp holds, and emergency stops. In this blog, we will detail the design and function of the parking brake in order to give you a better understanding of this often unappreciated component.
Like many other actuating parts of the aircraft, parking brakes use hydraulic pressure to maintain their position. However, the hydraulic pressure will eventually deplete to the point where it must be repressurized. The amount of time that the brakes may be left intact without needing to be repressurized varies between aircraft, but most commercial jets may effectively hold for at least 12 hours before requiring reassessment. During routine operation, the valve controlling the flow of hydraulic fluid to the brake system is closed. Once the pilot switches the brake-control device to the "ON'' position, the valve opens to allow movement of the hydraulic fluid.
Most Boeing and Airbus jets feature a brake pressure gauge near the control switch. Before applying the brakes, the pilot should first check the hydraulic accumulator pressure by depressing the brakes with the engine running. If the pressure gauge comes back with a low result, they should continue to engage the brake and alert the maintenance crew of this discrepancy. After ensuring adequate pressure, the pilot may then flip the selector switch to the "ON" position. Once in place, the flight crew should recheck both brake and accumulator pressure to ensure proper hydraulic delivery.
In the event that the aircraft continues to move after the application of the parking brake, the pilot must re-engage the pedal brake until the issue is resolved. Most aircraft are designed to give priority to input from the pedal brake over the parking brake, but others require the switch to be set to the "OFF" position before functionality may be regained. Additionally, it is universally recommended not to use the parking brakes if their temperature exceeds that which is recommended in the operating manual. This is to prevent excess heat transfer between the brakes, hydraulic fluid, and seals.
If chocks are to be used, it is generally recommended to place a minimum of two chocks for every set of wheels, excluding those in the center. In order to maintain the highest level of control, the chocks should be placed in the front and back of the wheel. For situations with inclement weather or low visibility, the crew may elect to place an additional set of chocks on both outboard wheels. Regardless of the configuration, it is necessary for the ground and flight crew to maintain adequate communication.
If you are looking to upgrade or replace aircraft parking brake components, let the team at Stacked NSN provide you with a quick and competitive quote. At Stacked NSN, we aim to help customers maintain operational readiness by supplying high-quality aerospace components with rapid lead times. With an inventory of over 2 billion ready-to-purchase items, we are confident we can help you find the exact items you require. We invite you to browse the various part catalogs on our website or use our powerful search engine to filter by part number, type, manufacturer, NSN, or CAGE Code. Once you have found a part you are interested in, you may begin the purchasing process at any time using our Instant RFQ service.
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